Liquid hydrocarbon fuel burning engines are used in a wide variety of applications including automotive, transportation, marine, electricity generation and compressors. Such engines are often relatively inefficient and may emit significant quantities of pollutant gases and particles. This is of particular concern when the engines are used in built up areas, e.g. cities where the resultant pollution affects significant numbers of people, but is also of significant concern in other situations.
Liquid hydrocarbon fuels typically include a number of additives to improve the efficiency of combustion, reduce pollutant levels, modify combustion characteristics of the fuel and maintain engine cleanliness.
Dispersants and detergents, for example low molecular weight amines, are used to improve engine cleanliness. Additives which can reduce friction levels or otherwise improve efficiency in an engine are of particular interest as they can improve fuel economy. Even small improvements in efficiency would have massive impacts on a global scale.
One family of chemicals which it has been discovered has significant utility as fuel additives are alkanolamides formed by the reaction of fatty acids with diethanolamine (DEA). These additives are particularly suitable for use as additives to gasoline fuels but also may be suitable for use in other liquid hydrocarbon fuels, such as diesel. However, there is a significant problem with existing methods of manufacture of alkanolamides and the by-products formed thereby. It has been found that by-products are prone to form throughout the reaction process. A particularly significant impurity, bis-hydroxyethyl piperazine (BHEP), is formed via dimerisation of two DEA molecules. BHEP crystallizes out of the composition, particularly if present in concentrations of over 5000 ppm, though lower concentrations may also be problematic in some circumstances. This has significant implications in that, when the composition is used as a fuel additive, BHEP may block fuel inlets or cause other undesirable build ups in the engine. Additionally, crystallization of BHEP out of the composition may result in an end user perceiving problems with the composition as deposits of BHEP appearing in, for example, barrels of the composition would give the appearance of a contaminated or faulty batch, even if there would be no deleterious effects of the BHEP in use. Thus the effects of significant BHEP presence in an alkanolamide composition make it an undesirable constituent.
Accordingly, it is desirable to provide a composition comprising an improved alkanolamide, which contains a reduced amount of undesirable reaction by-products, particularly BHEP, and which will be suitable for use as a liquid hydrocarbon fuel additive.